Observation.

[Silverstreak]

Noted that there is a continual degradation of the undergrowth of all the nature reserves over the last couple of months , once thick unpenetrable undergrowth are thinning at a rather fast rate despite more than adequate rainfall during the month of Jun/July. Clear example of such rapid degradation are BTNR,USR, SBWR, KRP, TBHP, MF, Lornie Trail, Terenteng Trail, pipeline track under TTW , Sime track ,the spa area and Rifle Range link.

Is this thinning of the undergrowth an annual cycle or is it abnormal?

[Commander]

Besides the plants, I also observe that the butterfly population has been rather low during this period as well. Those of you who go out regularly may have noticed this? There are few species as well as fewer individuals of the species whenever I had the chance to go out to the nature reserves.

Strange phenomenon... :hmmm: Just hope that it's the usual cyclic process that happens every year. The 3rd quarter of the year is usually a low time for butterflies, but this year seems to be especially so.

[Silverstreak]

Khew ,

Concur with



the butterfly population has been rather low during this period as well.

Did a trek recently thru Rifles Range link , the spa , Jelotong Tower, Sim Track and back thru the TTW pipeline ... total butts sighted hardly more than 20 including common browns and rings .

Another 4 hours Trek thru T15 at Mandai side only encountered less than 40 butts mainly skippers and a lone Silver-forget-me-not.

The lowest encounter rate since last september .... somedays hardly see any, other than skippers at shaded areas.:sweat:

Let's hope this is just a one-off seasonal Phenomenon .

[Silverstreak]

Took a trek on LT today, more butts activities after the rain.

sighted are yellow flash , banded yeoman, blue bottle, tailed judy, branded imperial, baron, common posy and some common skippers.

Hope the butterfly fairy has awaken from her slumber.:)

[Common Mime]

sighted are yellow flash , banded yeoman, blue bottle, tailed judy, banded imperial, baron, common posy and some common skippers.

Sunny, I believe you mean Branded Imperial, Eooxylides tharis distanti?

[Silverstreak]

Sunny, I believe you mean Branded Imperial, Eooxylides tharis distanti?

Never too late to correct an error .... :) Done!


Five years on and now you can walk into any of those forested area all over the island ..... and one can only speculate the impact of the thinning of undergrowth together with it a number of caterpillar hostplants !!

[WillFolsom]

I have noticed a shift in various species that I commonly found and photographed 10 years ago. I suspect global warming and other factors may play a role in this... no matter where you live. This, fortunately, is partially offset by those who are passionate about our natural world and who can sound the alarm to the right people if things go dreadfully wrong. You guys are cetainly in the forefront of the move to protect and preserve your natural resources. William

[teotp]

Monitoring change in the abundance and distribution of butterflies is a difficult task. A variety of methods have been used for surveying butterflies in tropical rainforest. Hand-netting data to calculate species richness and abundance of butterflies was used by Corbet (1941). Another method used by Fisher, Corbet and William (1943) which involves the empirical assumption of the distribution numbers of species represented by different numbers of individuals fits into a logarithmic series. Malaise and baited traps have been used by Owen (1969 & 1971) and Owen and Chanter (1972). Short-term studies using census techniques rely on identification of individuals on wing in small survey areas(100-500 sq. m.) was used by Bowman et al (1990) and Hill et al (1992). More recently, transect count method (also known as "Pollard walk" or transect walk method) have been used by many conservationists to estimate the richness and diversity for comparative surveys on butterflies in tropical rainforest (Walpole & Sheldon, 1999; Orr & Haeuser, 1996; Koh & Sodhi, 2004). Due to none of the above mentioned methods is perfect. The combined techniques that highlight the effectiveness of timed transects and hand-nets for monitoring tropical butterflies, and these two monitoring methods were used in conjunction with one another to provide best results (Sparrow et al, 1994; Caldas & Robbins, 2003). However, in addition to multiple monitoring techniques, long-term data are critical for true representations of butterfly biodiversity (Bonebrake et al, 2010). Factors influence the counts include difficulty of specific identification of some butterflies, habitat variations within and between forest types. Transects are limited to ground-based surveys and may result in an under-estimation of canopy species. Time and period of survey and fluctuation of weather conditions, activities of other animals including predators, as well as movement of butterflies may vary between species to species in relation the adult food sources and mate availability.

Many reports and documents discussed the biodiversity crisis and estimated about 40, 000 insect species already gone extinct over the past 600 years, but only 70 have been documented and half of which were Lepidoptera (Dumm, 2005; Bonebrake et al, 2010). The world contains roughly 18,000 - 20,000 species of butterflies with numbers highest in the tropics (Shields, 1989; Kristensen, 1998; Larson, 2005; Pogue, 2009). It is difficult to give a precise estimate of how many butterfly species are tropical because of the continual updating of checklists and splitting and lumping of species worldwide (Bonebrake et al, 2010).

The threats to tropical butterflies diversity can be categorised under the following headings:

1. Habitat loss: The most common habitat lost including conversion to agriculture, logging or fragmentation. Koh (2007) examined 20 studies on the impacts of land use, changes and habitat loss on butterfly biodiversity in South East Asia. He found that 7 of the studies showed decreased diversity in disturbed sites as compared to protected forests, but 9 studies showed the opposite trend. Hill and Hamer (2004) indicated that studies at small spatial scales are most likely to report increases in diversity when comparing disturbed and undisturbed sites than are studies at larger spatial scales. The reasons are likely that sampling artifact of species pooling, such that at smaller spatial scales rare or patchy species are more likely to detected differentially among sites of varying habitat loss pressures, and the time interval between the disturbance event and butterfly sampling could also affect the findings. On a large scale surveillance of West Africa, Larson (2008) found that no butterfly species are known to have gone extinct over the past 150 years, despite over 80% destruction of the forest in the area. Conversely, deforestation over 183 years in Singapore led to the recorded extinctions of 38% of butterfly species in Singapore (Ref.: Brook, B. W., N. S. Sodhi & P. K. L. Ng. Catastrophic extinctions follow deforestation in Singapore. Nature 424: 420-423, 2003.). In another report on the diversity of butterflies and host plants with particular reference to Singapore also pointed out the number of extinct butterfly species is expected to increase exponentially with the extinct of host plants (Ref.: Koh, L. P., N. S. Sodhi & B. W. Brook. Co-extinctions of tropical butterflies and thier hostplants. Biotropica 36, no.2: 272-274, 2004.). This is why Bonebrake and co-workers (2010) pointed out that how little we know about the effects of habitat loss processed on butterfly communities.

2. Global climate change: As indicated by Thomas and colleagues (2004), the effects of weather change over the next several decades are predicted to be significantly impact on populations worldwide, and are already being felt in many insect taxa, butterflies are certainly no exception and climate change effects have been seen among many temperate butterfly populations (McLaughlin et al, 2002;, Parmesan & Yohe, 2003; Parmesan, 2006). There are currently few additional empirical studies linking changes in weather to distribution changes or extinction in tropical Lepidoptera (Bonebrake et al, 2010). Theory and studies show that tropical insects in general should have smaller thermal niches than temperate ones based on the low annual thermal variability (Janzen, 1967; Ghalambor et al, 2006). However, temperature is not the only climate variable predicted to change as a result of climate change. Changes in rainfall can have large effects on tropical butterfly populations. For example, change in El Nino Southern Oscillation (ENSO) are likely to affect butterfly populations and migratory behaviour. Forest fire* also another factor should be considered. Furthermore, climate change is predicted to disrupt butterfly species interactions because of the close relationship among butterflies, their hostplants and other species (e.g. parasitoids), and may have ramifications for butterfly abundances and distributions as well.

3. Invasive species: After habitat loss and development, the invasion of non-native species can lead to distruption in species interactions involving butterfly systems. For example, the invasion of Chromolaena odorata, an understory hercaeous plant into logged sites of dry tropical forest in Thailand caused a shift in butterfly pollination activity away from the native canopy flowers to the understory (Ref.: Ghazoul, J. Impact of logging on the richness and diversity of forest butterflies in a tropical dry forest in Thailand. Biodiversity & Conservation 11: 521-541, 2002.). In this case, the effect of the non-native species facilitated by habitat loss through logging and represents a likely route through which invasive species may affect native populations in tropics (Bonebrake et al, 2010).

4. Toxins: There are reports on the effects of anthropogenic toxins distruptive to butterfly development and survival which include pesticides, herbicides, pollution and genetically modified organisms (e.g. Bacillus thuringiensis and baculovirus), but more studies are required to prove their threats to tropical butterfly biodiversity (Marvier et al, 2007;Bonebrake et al, 2010).

5. Exploitation and harvest: Some of the largest and/or most beautiful butterflies (e.g. Ornithoptera, Trogonoptera, Morpho) inhabit tropical forests, they appeal to commercial collectors has resulted in very large populations declines, leading to endangerment for these butterfly species.

Teo T P

* Also the impacts of other natural destructions like volcano eruption, earthquake and tsunami.

[Silverstreak]

Thank You Thiam Peng for a well thought out response, outlining the multiple threats butterfly faces, the difficulty in censor/survey and the limited knowledge and gaps of we know about butterfly!

:cheers:

[teotp]

Thank You Thiam Peng for a well thought out response, outlining the multiple threats butterfly faces, the difficulty in censor/survey and the limited knowledge and gaps of we know about butterfly!

:cheers:

Not at all Sunny. My apology for my late reply.

Teo T P

[Sunbeam]

I visited Mindanao, KK and southern parts of Mainland China this year. I also found that butterfly population is low this year in HK and these SE Asia areas. Some species come out much earlier than the usual seasons. Don't know whether it is caused by the La Nina effect.